It is well known that forage crops such as alfalfa, clover, bermuda grass, timothy grass, sudan grass and the like are of great nutritional value to farm animals, for example cattle and horses. In particular, these crops contain such nutritional constituents as digestible protein and sugar which provide energy. Consequently, such crops are harvested with a view to storing the harvested crop for later use as foodstuff during the nongrowing or winter months. It is most important therefore that after cutting the forage material and during storage, degradation is reduced to a minimum so as to preserve the high nutritive value of the freshly cut forage material.
In the past, several techniques have been employed in the cutting and drying of forage crops. A widely practiced technique is that of cutting and conditioning the crop and leaving it to dry on the field. The drying period is usually from 2 to 3 days but can be longer, for example from 5 to 6 days, depending on the prevailing temperature, wind and cloud conditions. During the drying period, the cut crop may be raked and left in windrows to dry further. When the water content of the crop has reached an acceptably low level, usually in the range 10 to 20% by wet weight or less, the dried crop, now referred to as "hay", is baled and stored, usually in a barn. If the water content of the crop is not reduced to a satisfactory low level, usually 10 to 20% by weight or less, bacterial and fungicidal growth will take place. This will not only cause spoilage and decreased nutritive value of the hay, but also may generate sufficient heat to cause autocombustion, thereby giving rise to a serious fire hazard.
A principle disadvantage of the harvesting technique described above is the problem of rainfall which may extend the drying period, which as indicated above may be as long as 6 days depending on the prevailing weather conditions. In this event, the cut crop remains damp for longer periods of time which, in turn, increases the chances of spoilage before the crop has dried. Prolonged exposure and additional raking or turning of rained-on-hay also substantially reduces the harvested yield of hay. Once the cut crop begins to spoil, the value of the crop as a foodstuff form farm animals is substantially reduced, and eventually the crop becomes completely unacceptable for that purpose.
The early U.S. Pat. No. 1,816,998 to Cushman discloses a method for accelerating the drying of freshly cut alfalfa and similar vegetable material in which the alfalfa is crushed immediately after cutting while still fresh and green to force the natural juices from the cells of the plant to the outside where they can evaporate more rapidly. The crushed leaves and stems are loosely distributed on the field and drying to an acceptable moisture content is generally completed within 12 to 18 hours. While this accelerated drying time is important, the major problem with this technique is the difficulty of raking and collecting the crushed material when dry. Generally, rakes are not designed to collect such finely crushed material and, thus, it is almost impossible to economically collect the crushed forage off the stubble.
U.S. Pat. No. 2,607,688 to Peebles et al discloses a process for reducing the extent of degradation of nutritive value of alfalfa and like materials which occurs during drying. In the process the freshly cut alfalfa is chopped and subjected to an acid and heat treatment which causes coagulation of the protein in the chopped alfalfa. The material is then subjected to mechanical pressure in an expeller which expresses the natural juices but causes the carotene to remain in the material.
U.S. Pat. No. 2,942,976 to Kosch describes a method of pelleting roughage crops such as alfalfa and similar crops, in which the severed forage is shredded in a chopper or hammermill, dehydrated and then formed into pellets. The shredding step reduces the forage to a form in which most of the stems and leaves are intact but have been reduced to short lengths.
Published British Pat. No. 2,019,731 to Krutz describes an apparatus for macerating forage products to enhance drying in a reduced period of time. The freshly cut forage is macerated by being passed between two rotating serrated rollers operated at different rotational speeds with respect to each other. The resulting macerated product is formed into a mat by pressure between a roller and a conveyor belt, and the mat is then deposited on the field for drying. The maceration is said to shear and shred the stems and leaves so as to expose more surface area for faster drying and to promote interweaving of the fibrous material to form a mat. During the mat formation, juices are expressed from the material by pressure between the roller and the conveyor belt, and these juices are collected by passage through perforations in the conveyor system but are not subsequently used.
The Krutz approach has two serious disadvantages. First, if a large proportion of the juices are expressed during mat formation, the nutritive value of the forage is seriously reduced. On the other hand, if large proportions of the juices are not expressed during mat formation, a wet (heavy) and non-cohesive mat results and the mat will not be in a mat-sustaining form. Furthermore, a wet mat will significantly disrupt the interweaving of the macerated material into a shape-sustaining mat. The wet mat is thus poorly formed and has a tendency to distort and fall apart during the drying stage, which increases the drying time. In addition, a poorly formed mat is difficult to collect after drying.